U.S. patent number 6,276,823 [Application Number 08/770,888] was granted by the patent office on 2001-08-21 for method for desuperheating steam.
This patent grant is currently assigned to Komax Systems, Inc.. Invention is credited to Leonard Tony King.
United States Patent |
6,276,823 |
King |
August 21, 2001 |
Method for desuperheating steam
Abstract
A desuperheater for reducing the superheated state of steam
located within a cylindrically-shaped conduit. The desuperheater
injects water droplets counter to the direction of moving
superheated steam within the conduit. Downstream of the water
droplet outlet is a biscuit which is aligned along the longitudinal
axis of the conduit to provide a series of separate mixing elements
all inducing the same rotational sign to fluids passing
therethrough.
Inventors: |
King; Leonard Tony (Long Beach,
CA) |
Assignee: |
Komax Systems, Inc.
(Wilmington, CA)
|
Family
ID: |
24259304 |
Appl.
No.: |
08/770,888 |
Filed: |
December 20, 1996 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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565591 |
Nov 30, 1995 |
|
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Current U.S.
Class: |
366/181.5;
366/339 |
Current CPC
Class: |
B01F
5/0461 (20130101); B01F 5/0614 (20130101); F22G
5/123 (20130101); B01F 5/0451 (20130101); B01F
2005/0637 (20130101) |
Current International
Class: |
F22G
5/00 (20060101); F22G 5/12 (20060101); B01F
005/06 () |
Field of
Search: |
;366/167.1,173.1,174.1,175.2,181.5,336-340 ;48/189.4
;138/37,40,42 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cooley; Charles E.
Attorney, Agent or Firm: Wittenberg; Malcolm B.
Parent Case Text
This is a continuation of application Ser. No. 08/565,591 filed
Nov. 30, 1995 now abandoned entitled. "DESUPERHEATER".
Claims
I claim:
1. A method for desuperheating steam having an initial amount of
superheat located within a cylindrically-shaped conduit, said
conduit having a longitudinal axis and circular cross-section, said
desuperheater providing for injecting water droplets within a
directionally moving stream of superheated steam, said
desuperheater comprising a biscuit which is aligned along said
longitudinal axis, said biscuit possessing an upstream face and
downstream face and a plurality of openings where within said
openings are located mixing elements which induce a rotational
angular velocity to the superheated steam and water droplets
passing therethrough, said desuperheater being further
characterized such that all of said mixing elements induce the same
rotational sign to said superheated steam and water droplets
passing therethrough, said biscuit supporting a frustum of a cone
emanating from the upstream face thereof and aligned along said
longitudinal axis, a feed leg radially emanating from the side wall
of said conduit downstream of said frustum which is in fluid
communication with a bore located within said biscuit along said
longitudinal axis thereof, said method further comprises passing a
stream of water through said feed leg and bore located within said
biscuit along said longitudinal axis thereof and discharging said
stream of water through said bore in the form of water droplets in
a direction counter to said directionally moving stream of
superheated steam and passing said superheated steam and water
droplets through said plurality of openings and mixing elements
located therein whereupon said combination of water droplets and
superheated steam are caused to assume a rotational angular
velocity resulting in a dropping of the amount of superheat from
said initial superheat amount.
Description
TECHNICAL FIELD OF THE INVENTION
The present invention deals with a device known as a desuperheater.
It has long been known that superheated steam is an excellent
source of energy but for certain applications saturated steam or
steam with only limited superheat is sought. As such, the present
invention deals with an improved device for reducing the
superheated state of steam to an acceptable value.
BACKGROUND OF THE INVENTION
When steam is manufactured from water, its temperature remains the
same as that of the water. There is a specific relationship between
steam temperature and pressure under saturation conditions. As
such, saturated steam can only acquire energy by removing the steam
from direct contact with water and by adding more heat to the body
of steam as in a boiler superheater. As an example, steam might be
generated at a temperature of 600.degree. F. and a pressure of 300
psi which corresponds to about 190.degree. of superheat. A typical
application at the utilization point of the steam could be a tube
and shell heat exchanger which works most efficiently if most of
the steam superheat is removed before it enters the exchanger so
that the steam may give up its heat of condensation. If not done,
the steam will simply pass through the exchanger as a gas and very
little heat transfer to the exchanger tubes will take place. In
such an application, residual superheat of approximately 10.degree.
F. could be tolerated while other devices may tolerate higher
degrees of superheat making precise temperature control easier.
A wide variety of desuperheater designs are available. Most of
these cool or desuperheat steam by injecting a water spray into the
steam pipe in the same direction as the steam flow. For example,
Copes--Vulcan produces a number of desuperheating configurations.
Perhaps the most straightforward design is a simple mechanical
atomizing type desuperheater which consists of a main tube and
spray nozzle. Cooling water flows through the main tube to the
nozzle, which injects water droplets in the direction of steam flow
in an attempt to achieve rapid absorption of the liquid water.
Another type of desuperheater consists of a steam atomizing device
which includes a spray head having a series of nozzles arranged in
a circle. Atomizing steam from a higher pressure source is
introduced through the steam ports of the device at right angles to
the radial cooling water holes thereby blasting each of the cooling
water jets. The cooling water is projected at high velocity with
small droplet size into the steam header where it is distributed
and vaporized.
Yet another type of desuperheater is provided with a variable
orifice consisting of a housing with self-regulating orifice. This
orifice is made up of a circular seat with a flow plug maintained
in concentric position by a plug guide. Cooling water enters the
orifice chamber and is uniformly distributed around its periphery.
The amount of water injected into the superheated steam is
controlled by a diaphragm operated valve actuated by a temperature
controller.
Generally, most prior art devices are situated in environments in
which steam velocities are in the range of 30 to 300 feet per
second. Nozzle spray patterns are often conical and nozzle water
velocities must be high for two reasons. Firstly, one must avoid
the steam momentum from collapsing the spray pattern into a central
core. As such, nozzle exit velocity must be much higher than the
steam velocity. Secondly, a high nozzle velocity must be maintained
over the water flow rate range in order to produce small water
droplets to give good contacting efficiency. As noted from the
above discussion, as efficiencies improve, nozzle configurations
become correspondingly more complex. Very high nozzle velocities
lead to the need for stellite nozzle construction to minimize
nozzle erosion. Pipe erosion can also be a problem and special
linings have been employed to cope with such situations.
It is thus an object of the present invention to provide a device
to improve the efficiency of desuperheaters regardless of the
various environments in which such devices are located.
It is yet a further object of the present invention to provide an
enhancement to desuperheaters in the form of a motionless mixing
apparatus having no moving parts and is thus not complex nor
subject to clogging or breakdown when used in severe
environments.
These and further objects will be more readily appreciated when
considering the following description and appended drawing in
which:
The sole FIGURE shows the device of the present invention in
cross-section.
SUMMARY OF THE INVENTION
A desuperheater for reducing the superheated state of steam located
within a cylindrically-shaped conduit. The conduit is provided with
a longitudinal axis and circular cross-section.
The desuperheater is provided for injecting water droplets within a
directionally moving stream of superheated steam. The desuperheater
comprises a biscuit which is aligned along the longitudinal axis,
the biscuit possessing an upstream face and downstream face and a
plurality of openings. Within the openings are located mixing
elements which induce a rotational angular velocity to the
superheated steam and water droplets passing therethrough. The
desuperheater is further characterized such that all of the mixing
elements induce the same rotational sign to the superheated steam
and water droplets passing therethrough.
The biscuit supports the frustum of a cone emanating from its
upstream face. The cone is aligned along the longitudinal axis. A
feed leg radially emanates from the side wall of a conduit
downstream of the frustum which is in fluid communication with a
bore located within the biscuit along the longitudinal axis for
discharge of a fluid stream of water droplets in a direction
counter to the directionally moving superheated steam, the
discharge of water droplets being from an opening located at the
apex of said frustum.
DETAILED DESCRIPTION OF THE INVENTION
Turning to the sole FIGURE, desuperheater 10 is shown located
within cylindrically shaped conduit 1. Alternatively, desuperheater
10 is provided with flanges 11 which can be used to attach to
corresponding flanges of suitable conduit as an add-on processing
element at any time desuperheating is required to reduce the
superheated state of steam passing therethrough.
Conduit 1 is provided with longitudinal axis 2 as well as a
circular cross-section. The desuperheater itself is provided for
injecting water droplets in a direction opposite to the flow of
superheated steam as shown in the FIGURE.
Desuperheater 10 comprises biscuit 20 possessing upstream face 21
and downstream face 22. The biscuit is also provided with a
plurality of openings 4 where within said openings are located
mixing elements 5 which induce a rotational angular velocity to the
superheated steam and water droplets passing therethrough.
The FIGURE shows mixing element 5 as being in the shape of a helix
inducing the same rotational angular velocity to superheated steam
contained within conduit 1 and water droplets emanating from
orifice outlet 9.
Downstream end 22 of biscuit 20 is generally of conical shape while
upstream end 21 is in the shape of a frustum of a cone. Both the
upstream and downstream ends of biscuit 20 are aligned with
longitudinal axis 2. As noted from viewing the figure, nozzle 8,
also in the general shape of a frustum of a cone, protrudes from
upstream end 21, nozzle end 8 also being aligned with longitudinal
axis 2.
As further noted from the FIGURE, feed leg 6 is shown radially
emanating from the side wall of conduit 1 located downstream of
upstream face 21 and nozzle 8. Through radial feed leg 6 is
provided fluid, generally liquid water in communication with bore 7
located within said biscuit along longitudinal axis 2 for discharge
of a fluid stream of water droplets in a direction counter to
directionally moving superheated stream as shown in the FIGURE.
As an alternative to helical mixing elements 5, one could employ
mixing elements such as those shown in applicant's U.S. Pat. Nos.
3,923,288 and 4,034,965, the disclosures of which are incorporated
by reference. These mixing elements include a central flat portion,
first and second ears, round or otherwise configured at their
outside periphery for a general fit into openings 4 and which are
bent upward and downward from the central flat portion. A second
pair of ears at the opposite side of the flat portion are also
provided again bent downward and upward respectively. Such elements
may be formed from a single flat sheet by a punch press, for
example.
Regardless of the specific mixing elements employed, it is
imperative in practicing the present invention that all mixing
elements induce the same rotational angular velocity to the
superheated steam and water droplets passing therethrough. As such,
when the superheated steam and water droplets pass along
longitudinal axis 2 of conduit 1, they eventually are passed into
contact with mixing elements 5 located within openings 4 which are
preferably symmetrically spaced about longitudinal axis 2. Ideally,
six such openings and corresponding mixing elements are provided in
a typical application symmetrically spaced about longitudinal axis
2. When the fluids are passed in contact with mixing elements 5, a
clockwise velocity vector or rotational vector is imposed if the
mixing elements of U.S. Pat. Nos. 3,923,288 and 4,034,965 are
employed, the flat portion of each mixing element transforms the
rotational vector to a lateral or radial vector. Subsequent to the
flat portion, the ear elements impose a further clockwise velocity
vector adding somewhat to the lateral or radial vector. The ears
also impose a substantially inward directed radial velocity vector
on materials moving longitudinally whereas the remaining pair of
ears impose a substantially outward directed radial velocity
vector. When six equally sized and spaced openings 4 are provided,
flow through conduit 1 is divided 12 ways and exits as six streams
all violently rotating in the same direction. This produces six
primary and many secondary impingement mixing zones at the exit of
biscuit element 20 giving excellent contacting between the water
droplets and the superheated steam.
It is noted that most conventional superheaters require a long
length of pipe downstream to effect the proper mixing and
contacting of steam and water which is testimony to their poor
contacting efficiencies. By contrast, the desuperheater of the
present invention requires only a short distance between the exit
of biscuit 20 and a downstream temperature sensor.
Desuperheaters of the present invention have proven to be highly
efficient while exhibiting rather low pressure drops. Specifically,
the pressure drop of a desuperheater of the present invention is
characterized by the following equation:
where:
For example, for a steam pressure of 50 psig (65 psia), a steam
flow rate of 3500 lb/hr and pipe size of 8 inches, the pressure
drop across the present desuperheater would be only 0.03 psi.
Furthermore, the water flow rate requirements required for a given
reduction of superheat compares favorably to desuperheaters of the
prior art. Specifically, water flow rate requirements for the
desuperheater of the present invention can be depicted by the
following equation:
where:
(wherein Enthalpy values can be taken from steam tables or from a
Mollier diagram).
As an example of the water flow rate requirements of the present
invention, given a steam flow rate of 25,000 lb/hr entering the
present desuperheater at a pressure of 235 psig (250 psia) and at a
temperature of 600.degree. F., if the pressure drop through the
desuperheater is 5 psi, the water flow rate required to produce an
exit temperature of 410.degree. F. would be:
As further noted above, it is a design criteria that water droplets
emanating from nozzle outlet 9 be directed upstream against the
directional flow of superheated steam. As such, the axial velocity
from the spray nozzle must stop and reverse. As such, the maximum
velocity which water droplets can achieve is no greater than the
surrounding superheated steam velocity.
In view of the foregoing, modifications to the disclosed
embodiments within the spirit of the invention will be apparent to
those of ordinary skill in the art. The scope of the invention is
therefore to be limited only by the appended claims.
* * * * *